1. Field of the Invention
The present invention relates to a radiation image recording and reproducing method, and more particularly, to a radiation image recording and reproducing method employing a divalent europium activated alkaline earth metal halophosphate phosphor.
2. Description of the Prior Art
For obtaining a radiation image, there has been conventionally utilized radiography employing a combination of a radiographic film having an emulsion layer containing a photosensitive silver salt material and an intensifying screen. As a method replacing the above-mentioned conventional radiography, a radiation image recording and reproducing method employing a stimulable phosphor stated, for instance, in U.S. Pat. No. 4,239,968, has been recently paid much attention. The radiation image recording and reproducing method involves steps of causing the stimulable phosphor to absorb a radiation having passed through an object or having radiated from an object; exciting the phosphor with an electromagnetic wave such as visible light or infrared rays (stimulating rays) to release the radiation energy stored in the phosphor as light emission (stimulated emission); photoelectrically detecting the emitted light to obtain electric signals; and reproducing the radiation image of the object as a visible image from the electric signals.
In the radiation image recording and reproducing method, a radiation image is obtainable with a sufficient amount of information by applying a radiation to the object at a considerably smaller dose as compared with the conventional radiography. Accordingly, the radiation image recording and reproducing method is of great value, especially when the method is used for medical diagnosis.
The phosphor employable in the above-described method is a stimulable phosphor which emits light (gives a stimulated emission) when excited with an electromagnetic wave in the visible to infrared region after having exposed to a radiation such as X-rays. For such stimulable phosphor, there have been known a divalent europium activated alkaline earth metal fluorohalide phosphor (M.sup.II FX:Eu.sup.2+, in which M.sup.II is at least one alkaline earth metal selected from the group consisting of Mg, Ca and Ba; and X is at least one halogen selected from the group consisting of Cl, Br and I); an europium and samarium activated strontium sulfide phosphor (SrS: Eu,Sm); an europium and samarium activated lanthanum oxysulfide phosphor (La.sub.2 O.sub.2 S:Eu,Sm); an europium activated barium aluminate phosphor (BaO.Al.sub.2 O.sub.3 :Eu); an europium activated alkaline earth metal silicate phosphor (M.sup.2+ O.SiO.sub.2 :Eu, in which M.sup.2+ is at least one alkaline earth metal selected from the group consisting of Mg, Ca and Ba); a cerium activated rare earth oxyhalide phosphor (LnOX:Ce, in which Ln is at least one rare earth element selected from the group consisting of La, Y, Gd and Lu; and X is at least one halogen selected from the group consisting of Cl, Br and I), and the like.